To transport natural gas from production sites to consumers, pipeline operators install large compressors at transport stations along the pipelines. Natural gas pipeline networks connect production operations with local distribution companies through thousands of miles of gas transmission lines. Typically, reciprocating gas compressors are used as the prime mover for pipeline transport operations because of the relatively high pressure ratio required. Reciprocating gas compressors may also be used to compress gas for storage applications or in processing plant applications prior to transport.
Reciprocating gas compressors are a type of compressor that compresses gas using a piston in a cylinder connected to a crankshaft. The crankshaft may be driven by a motor or an engine. A suction valve in the compressor cylinder receives input gas, which is then compressed by the piston and discharged through a discharge valve.
Reciprocating gas compressors inherently generate transient pulsating flows because of the piston motion and alternating valve motion. Various devices and control methods have been developed to control these pulsations. An ideal pulsation control design reduces system pulsations to acceptable levels without compromising compressor performance.
A specific challenge when using high-horsepower, high-speed, variable-speed compressors is pulsations in the cylinder nozzle. The cylinder nozzle is the section of pipe that connects the cylinder to the suction or discharge side of the compressor, typically to a filter bottle. This section of pipe can provide significant resonance responses. Currently, one solution to attenuating cylinder nozzle pulsations is the installation of an orifice in the cylinder nozzle. For example, a plate with a flow restricting hole may be placed across the circumference of the nozzle. However, a drawback to use of the orifice is that it causes a pressure drop that requires the supply of additional horsepower. This burden can be significant on large horsepower units.